.\" -*- nroff -*-
.\" Copyright (c) 2018      FUJITSU LIMITED.  All rights reserved.
.\" $COPYRIGHT$
.TH MPIX_Barrier_init 3 "Jun 10, 2020" "4.0.4" "Open MPI"
.SH NAME
\fBMPIX_Allgather_init, MPIX_Allgatherv_init, MPIX_Allreduce_init, MPIX_Alltoall_init, MPIX_Alltoallv_init, MPIX_Alltoallw_init, MPIX_Barrier_init, MPIX_Bcast_init, MPIX_Exscan_init, MPIX_Gather_init, MPIX_Gatherv_init, MPIX_Reduce_init, MPIX_Reduce_scatter_init, MPIX_Reduce_scatter_block_init, MPIX_Scan_init, MPIX_Scatter_init, MPIX_Scatterv_init, MPIX_Neighbor_allgather_init, MPIX_Neighbor_allgatherv_init, MPIX_Neighbor_alltoall_init, MPIX_Neighbor_alltoallv_init, MPIX_Neighbor_alltoallw_init\fP \- Builds a handle for a collective communication or neighborhood collective communication

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
#include <mpi-ext.h>
int MPIX_Allgather_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Allgatherv_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, const int \fIrecvcounts\fP[],
	const int \fIdispls\fP[], MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Allreduce_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP, int \fIcount\fP,
	MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Alltoall_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Alltoallv_init(const void *\fIsendbuf\fP, const int \fIsendcounts\fP[],
	const int \fIsdispls\fP[], MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP,
	const int \fIrecvcounts\fP[], const int \fIrdispls\fP[], MPI_Datatype \fIrecvtype\fP,
	MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Alltoallw_init(const void *\fIsendbuf\fP, const int \fIsendcounts\fP[],
	const int \fIsdispls\fP[], const MPI_Datatype \fIsendtypes\fP[], void *\fIrecvbuf\fP,
	const int \fIrecvcounts\fP[], const int \fIrdispls\fP[],
	const MPI_Datatype \fIrecvtypes\fP[], MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Barrier_init(MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Bcast_init(void *\fIbuffer\fP, int \fIcount\fP, MPI_Datatype \fIdatatype\fP,
	int \fIroot\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Exscan_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP, int \fIcount\fP,
	MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Gather_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, int \fIroot\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Gatherv_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, const int \fIrecvcounts\fP[],
	const int \fIdispls\fP[], MPI_Datatype \fIrecvtype\fP, int \fIroot\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Reduce_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP, int \fIcount\fP,
	MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP, int \fIroot\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Reduce_scatter_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP,
	const int \fIrecvcounts\fP[], MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP,
	MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Reduce_scatter_block_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP,
	int \fIrecvcount\fP, MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Scan_init(const void *\fIsendbuf\fP, void *\fIrecvbuf\fP, int \fIcount\fP,
	MPI_Datatype \fIdatatype\fP, MPI_Op \fIop\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Scatter_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, int \fIroot\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Scatterv_init(const void *\fIsendbuf\fP, const int \fIsendcounts\fP[],
	const int \fIdispls\fP[], MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP,
	int \fIrecvcount\fP, MPI_Datatype \fIrecvtype\fP, int \fIroot\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Neighbor_allgather_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Neighbor_allgatherv_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, const int \fIrecvcounts\fP[],
	const int \fIdispls\fP[], MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP,
	MPI_Info \fIinfo\fP, MPI_Request *\fIrequest\fP)

int MPIX_Neighbor_alltoall_init(const void *\fIsendbuf\fP, int \fIsendcount\fP,
	MPI_Datatype \fIsendtype\fP, void *\fIrecvbuf\fP, int \fIrecvcount\fP,
	MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Neighbor_alltoallv_init(const void *\fIsendbuf\fP,
	const int \fIsendcounts\fP[], const int \fIsdispls\fP[], MPI_Datatype \fIsendtype\fP,
	void *\fIrecvbuf\fP, const int \fIrecvcounts\fP[], const int \fIrdispls\fP[],
	MPI_Datatype \fIrecvtype\fP, MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

int MPIX_Neighbor_alltoallw_init(const void *\fIsendbuf\fP,
	const int \fIsendcounts\fP[], const MPI_Aint \fIsdispls\fP[],
	const MPI_Datatype \fIsendtypes\fP[], void *\fIrecvbuf\fP,
	const int \fIrecvcounts\fP[], const MPI_Aint \fIrdispls\fP[],
	const MPI_Datatype \fIrecvtypes\fP[], MPI_Comm \fIcomm\fP, MPI_Info \fIinfo\fP,
	MPI_Request *\fIrequest\fP)

.fi
.SH DESCRIPTION
.ft R
Creates a persistent communication request for a collective operation or neighborhood collective operation.

As of Nov. 2018, the feature of persistent collective communication operations and persistent collective neighborhood communication operations is planned to be included in the next MPI Standard after MPI-3.1.
.nf

    https://github.com/mpi-forum/mpi-issues/issues/25
.fi

Open MPI implements 2018 Draft Specification of the MPI standard shown in the following URL.
.nf

    https://www.mpi-forum.org/docs/drafts/mpi-2018-draft-report.pdf
.fi

The interface may still change in the standard. Therefore the prefix \fIMPIX_\fP is used instead of \fIMPI_\fP for these request creation routines. To start, complete, and free the created request, usual MPI routines (\fIMPI_Start\fP etc.) can be used.

Future versions of Open MPI will switch to the \fIMPI_\fP prefix and will not require the C header file \fImpi-ext.h\fP, the Fortran modules \fImpi_ext\fP and \fImpi_f08_ext\fP, and the Fortran header file \fImpif-ext.h\fP once the MPI Standard which includes this feature is published.

.SH EXAMPLE
.nf

    MPI_Request req;
    MPIX_Barrier_init(MPI_COMM_WORLD, MPI_INFO_NULL, &req);
    MPI_Start(&req);
    MPI_Wait(&req, MPI_STATUS_IGNORE);
    MPI_Request_free(&req);
.fi

.SH SEE ALSO
.ft R
.sp
MPI_Start
.br
MPI_Startall
.br
MPI_Request_free
